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Why must conservators limit moisture when treating drawings on paper?

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Inside the ongoing preservation of the Vatican — Art conservation and restoration Learn about the restoration of tiles in St. Peter's Basilica, Vatican City.

In the field of art conservation and restoration, conservators must carefully limit the use of moisture when treating drawings on paper because of the unique, absorbent nature of the medium.

Unlike paintings on canvas, which consist of distinct, laminated layers, paper and its colorants—such as inks, washes, and pencils—form an inseparable amalgam. Because these materials are incorporated directly into the fibrous texture of the paper, the application of moisture during procedures like washing or stain reduction carries significant risks. Conservators must assess the specific tolerance of the individual drawing media and the subtle qualities of the paper before proceeding, as excessive moisture can cause damage to the artwork's integrity. Consequently, immersion in water baths is reserved only for the most stable situations to avoid unintended chemical transfer or image offset.1